Project Summary/Abstract The basic molecular mechanisms associated with Alzheimer?s disease (AD) remain a critical knowledge gap that prevents identification of effective therapeutic targets and diagnostic/prognostic biomarkers. The current proposal will address this gap by studying the role of signaling pathways associated with AMP-activated protein kinase (AMPK) isoforms in AD. AMPK functions as a central cellular energy sensor to maintain energy homeostasis. Moreover, AMPK is a nexus to incorporate multiple signaling pathways for de novo protein synthesis (mRNA translation). Importantly, both disruptions in energy homeostasis and impairments in de novo protein synthesis are implicated in cognitive syndromes associated with neurodegenerative diseases, including AD. The kinase catalytic subunit of AMPK exists in two isoforms in brain: ?1 and ?2, and their roles in synaptic plasticity and memory are unknown. We generated brain- and isoform-specific conditional AMPK?1 and ?2 knockout mice (AMPK?1 cKO and AMPK?2 cKO), and performed behavioral, electrophysiology, imaging, and biochemical tests to characterize isoform-specific phenotypes. Driven by our preliminary data, our central hypothesis is that disruption of AMPK isoform homeostasis represents a key molecular mechanism underlying AD-associated impairments of synaptic plasticity and memory defects. Three specific aims are formulated to test the hypothesis. Aim 1 seeks to identify isoform-specific roles of AMPK in hippocampal synaptic plasticity and memory formation. Aim 2 is designed to determine AMPK isoform-specific regulation of synaptic failure and memory impairment in Tg19959 AD mouse model. Aim 3 is designed to elucidate AMPK isoform-specific effects on de novo protein synthesis and brain A? pathology in Tg19959 AD mouse model. The project proposes in-depth analyses using multiple state-of-art methods in neuroscience and AD, including mouse genetics, synaptic electrophysiology, confocal imaging, and behavioral tests. Moreover, novel methods to measure de novo protein synthesis combined with mass spectrometry/proteomics approach will be applied to reveal identities of proteins in AD brains whose synthesis is dysregulated because of abnormal signaling due to disruption of AMPK isoform homeostasis. This multidisciplinary approach will enable us to identify detailed cellular/molecular mechanisms associated with aberrant AMPK signaling in AD pathogenesis, providing insights into novel therapeutic targets and diagnostic biomarkers for AD and other dementia syndromes.